We tried a lot of different SMA-Male to N-Female adapters before deciding that none of them were good enough and started making our own instead. These adapters use high-quality .141 semi-flexible cable that is durable and strong, and unlike most other adapters won't fall apart during installation.
This is a 50 Ohm impedance adapter (both N-type and SMA connectors are 50-ohm connectors).
The .141 cable has a silver-plated solid copper center conductor, PTFE dielectric, a silver-plated copper braid, and a blue FEP jacket.
The high quality materials allow for greater than 100dB shielding, and this high quality adapter is rated for use at frequencies of up to 12 GHz.